1. Field of the Invention
The present invention relates to a spot-type disc brake, in particular for a motor vehicle, with a housing comprising a housing bridge, a first housing leg having an actuating unit and a second, outboard housing leg. In this arrangement, each one brake shoe with brake lining and back plate, acting upon a brake disc, is fitted at the inside surfaces of the housing legs. The housing and the brake shoes are slidably mounted on a mounting support on the vehicle in the direction of an axis of movement of the actuating unit. Further, a hold-down spring is provided on the side of the actuating unit between an abutment surface in the housing bridge and the brake shoe, the said spring preloading the brake shoe in relation to the mounting support and the abutment surface in order to prevent the brake shoe from rattling on the mounting support.
2. Description of the Prior Art
DE 25 58 141 A1 discloses a corresponding spot-type disc brake, which includes a piston-and-cylinder unit as actuating unit. When the brake is operated, the piston moves out of the cylinder and pushes the piston-side brake shoe against the brake disc until it abuts thereon. Now the piston-and-cylinder unit and the piston-side housing leg, respectively, moves away from the brake disc and pulls the opposite housing leg in the direction of the disc side there. As a result, the other brake shoe is also pressed against the brake disc, and both brake shoes exert a normal force on the brake disc. When the brake is released, hydraulic pressure does not prevail in the piston-and-cylinder unit, and the brake shoes exert no longer normal force on the brake disc. However, they still bear against the brake disc and, induced by friction, produce a residual brake torque, the so-called residual moment. In addition, the pads are thermally loaded to an increased degree, because no air flow develops between pad and disc, and pad and disc are not uncoupled thermally.
In view of the above, an object of the invention is to disclose a spot-type disc brake with a hold-down spring, which exhibits an improved clearance behavior of the brake shoes, that means that the residual moment is reduced and, further, pad and disc are uncoupled thermally.